Physiological responses to acute temperature increase in European eels Anguilla anguilla infected with Anguillicola crassus. (1/6)

The swimbladder parasite, Anguillicola crassus has infected, and spread rapidly, through European eel Anguilla anguilla (L.) populations over the past 20 to 25 yr. Our aim in the present studies was to elucidate whether the presence of A. crassus in these eels alters their rapid physiological responses to an acute temperature increase, compared to the response of uninfected fish. Both infected and uninfected fish showed significant increases in plasma cortisol after 2 h at a raised environmental temperature with increased plasma glucose after 6 h. However, infected eels exhibited a slight lag in glucose mobilisation, which may be due to the metabolic cost of harbouring a sanguiverous parasite. Both infected and uninfected fish showed a significant increase in haematocrit after 6 h of temperature elevation, but only uninfected fish exhibited a significant increase in haemoglobin at this point. However, there were no significant changes in mean erythrocyte haemoglobin concentration in either group. Our results suggest that acute temperature increase alone is unlikely to cause significant mortality of A. crassus-infected European eels; however, the effects of chronic increases in temperature in combination with other factors such as toxicants and hypoxia requires examination.  (+info)

Phylum-wide analysis of SSU rDNA reveals deep phylogenetic relationships among nematodes and accelerated evolution toward crown Clades. (2/6)

Inference of evolutionary relationships between nematodes is severely hampered by their conserved morphology, the high frequency of homoplasy, and the scarcity of phylum-wide molecular data. To study the origin of nematode radiation and to unravel the phylogenetic relationships between distantly related species, 339 nearly full-length small-subunit rDNA sequences were analyzed from a diverse range of nematodes. Bayesian inference revealed a backbone comprising 12 consecutive dichotomies that subdivided the phylum Nematoda into 12 clades. The most basal clade is dominated by the subclass Enoplia, and members of the order Triplonchida occupy positions most close to the common ancestor of the nematodes. Crown Clades 8-12, a group formerly indicated as "Secernentea" that includes Caenorhabditis elegans and virtually all major plant and animal parasites, show significantly higher nucleotide substitution rates than the more basal Clades 1-7. Accelerated substitution rates are associated with parasitic lifestyles (Clades 8 and 12) or short generation times (Clades 9-11). The relatively high substitution rates in the distal clades resulted in numerous autapomorphies that allow in most cases DNA barcode-based species identification. Teratocephalus, a genus comprising terrestrial bacterivores, was shown to be most close to the starting point of Secernentean radiation. Notably, fungal feeding nematodes were exclusively found basal to or as sister taxon next to the 3 groups of plant parasitic nematodes, namely, Trichodoridae, Longidoridae, and Tylenchomorpha. The exclusive common presence of fungivorous and plant parasitic nematodes supports a long-standing hypothesis that states that plant parasitic nematodes arose from fungivorous ancestors.  (+info)

Wnt signaling induces vulva development in the nematode Pristionchus pacificus. (3/6)

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Behavioural genetics: worms seek that old beetle smell. (4/6)

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Evolution of a new sense for wind in flying phasmids? Afferents and interneurons. (5/6)

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A gonad-derived survival signal for vulval precursor cells in two nematode species. (6/6)

Intercellular cell-survival signals play a major role in animal development [1]. In the nematode Caenorhabditis elegans, however, the stereotyped cell deaths that occur reproducibly during development are regulated in a cell-autonomous fashion (or, in a few cases, by a death-inducing signal) [2]. We show here the existence of a cell-survival signal acting on the vulval precursor cells in two nematodes, Turbatrix aceti and Halicephalobus sp. JB128. In C. elegans [3], as in many other nematode species [4] [5-7], ablation of the gonad causes all vulval precursor cells to adopt a default epidermal fate: a gonadal signal is required for the induction of vulval fates. In the nematodes T. aceti and Halicephalobus sp. JB128, however, we found that ablation of the gonad in the L1 larval stage caused all vulval precursor cells to undergo programed cell death. Thus, in intact Turbatrix and Halicephalobus, a survival signal from the gonad prevents activation of the cell-death program in vulval precursor cells. Our results demonstrate the existence of intercellular cell-survival signals in nematodes and uncover an evolutionary variation in the role of the gonad in nematode vulval development.  (+info)